Use of GPUs. Not Talos II it seems (?), but with POWER, GPUs are first-class citizens on the system, with NVLink-2-bus access to main memory as the CPU - 150 GB/sec in each direction! (simultaneously!)
Actual GPU use on Talos seems to be problematic from their wiki page. The CUDA use case is supported, but that bandwidth seems too high. Or are you quoting some future number ? The current bandwidth on a P9 system with nvlink is closer to 30 GB/s. And I don't think Talos supports nvlink.
Are all accesses to the memory from the GPU still checked for permissions at the hardware level by an IOMMU?